The disclosure relates to a printed circuit board, and more particularly to a printed circuit board, which includes a circuit pattern having a curved surface in a portion of a lateral side thereof and a surface treatment layer formed through electrolytic plating, and a method of fabricating the same.
A printed circuit board (PCB), which is formed by printing a circuit line pattern on an electrically insulating substrate using a conductive material, such as copper (Cu), signifies a board immediately before electronic components are mounted thereon. That is to say, the PCB signifies a circuit board in which the mounting positions of the electronic components are determined, and circuit patterns are printed on and fixed to the surface of a flat plate to connect the electronic components with each other, in order to densely mount various types of electronic devices on the flat plate.
In general, for the surface treatment of the circuit patterns formed on the PCB, Organic Solderability Preservative (OSP) has been used, and electrolytic nickel/gold, electrolytic nickel/gold-cobalt alloy, or electroless nickel/palladium/gold has been used.
In this case, various surface treatment schemes may be employed according to the use purposes thereof. For example, the surface treatment schemes for soldering, wire-bonding, and a connector may be used.
FIG. 1 is a sectional view showing a PCB according to the related art.
Referring to FIGS. 1(a) and 1(b), the PCB includes an insulating layer 10, a plating seed layer 20, a circuit pattern 30, a protective layer 40, a first surface treatment layer 50, and a second surface treatment layer 60.
FIGS. 1(a) and 1(b) show the insulating layer 10, the plating seed layer 20, the circuit pattern 30, the first surface treatment layer 50, and the second surface treatment layer 60 having the same structures except for protective layers 40 having different structures according to the used shape thereof.
In other words, the protective layer 40 shown in FIG. 1(a) covers the entire exposed surface of the insulating layer 10 while covering at least a portion of a top surface of the circuit pattern 30, and has a shape of protruding upward from the surface of the second surface treatment layer 60.
The protective layer 40 shown in FIG. 1(b) serves only as an embankment. Accordingly, the protective layer 40 exposes at least a portion of the surface of the insulating layer 10 in the state that the protective layer 40 does not make contact with the circuit pattern 30.
Meanwhile, the above PCB according to the related art includes the first surface treatment layer 50 including nickel (Ni) and the second surface treatment layer 60 including gold (Au) for the surface treatment of the circuit pattern 30.
In this case, the first surface treatment layer 50 and the second surface treatment layer 60 are generally formed through electroless plating since a seed layer for electroplating does not separately exist.
In addition, to form the first and second surface treatment layers 50 and 60 through the electrolytic plating, a plating seed layer must be additionally formed.
However, design limitations may exist as the additional seed layer is formed in order to perform the electroplating even though the surface treatment of the PCB is generally performed through the electroless plating.
In addition, the surface treatment of the PCB essentially requires the formation of the first surface treatment layer 50 including metal, such as Ni, for the diffusion of the circuit pattern 30 including Cu.